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Timming Chain inquiry

Ewenm

NAXJA Forum User
hi

i have a 1994 xj limited l6 ( export model) and am wondering how a stretched timing chain might effect performance

I've owned my car since it was three years old so am aware of how it used to perform, with that said and with 400,000 kilometres on the clock i realise its no longer new.

the compression is all around 135 psi, the back cylinder a little lower from memory 128

a vacuum gauge reads a little low indicating worn rings.

i have 31 inch tyres but have regard to 4.10 gears back and front

the car has great standing start acceleration but then drops off around 2000/2500 rpm, while cruising on the highway it runs well and gets reasonable fuel economy.

but in hilly country it lacks some punch.

so I'm wondering if a stretched chain could retard the cam enough to effect it this way

i did the take out the plugs and rotate the crankshaft back and forth to try and gauge how much slop there was in the chain by watching the effect on the distributor rotor button, but that was inconsistent, my helper didn't under stand what we were looking for.

so again will a stretched timing chain allow for good pickup down low but average to poor performance up high

what do you think, i also have the standard rear main seal leak ( has been ever since i owned the car) and the front seal weaps, the harmonic balancer damper rubber is showing very slight signs on bulging so its not unreasonable of me to do a job on the sump etc, trouble is I'm 62 and finding crawling under cars not that attractive any longer heheheh

thanks for reading

Ewen
 
When I had the head off my 97 XJ because of a weak head gasket I went through and resealed the bottom end while the machine shop was working on the head. I found the timing chain at/nearly at the service limit so I changed it. I think it may have idled smoother afterwards but I don't remember anymore. A lot of folks with earlier Jeeps comment on grunt off the line but poorer top end. Mine is the same performance wise, and a new chain provided no perceptible difference. I also have a 01 XJ which seems slower off the line but has more top end. It could be related to different head designs. Compression on both engines is around 145-160 psi. I believe a stretched chain would retard timing & would give you better low end. How much improvement you'll see is based on how much the chain is stretched. I've found that after a valve job compression comes up 10-15 psi. If you do both a wet and dry compression check and there isn't much difference, it may be your valves not the rings lowering your compression. My 2001 has 337,000 miles on the original chain and apart from a rear main seal leak I don't think the engine runs any differently than it did new (it has had head work at 160,000 - carboned up valves causing stumbling and at 315,000 miles for a crack...)
 
thanks for the response, i also should have said i had the head done about 12 years ago, i overheated it, didn't realise the declutching fan was just free wheeling, i got stuck in heavy traffic and a fortnight later had rough idle etc.

being a '94 its always been a bit rattly at idle but of late I've noticed a sort of rattly noise under load ( not detonation) like maybe the TC is rattling under load, mainly happens when towing my boat when i have to slow down and accelerate around corners/intersections etc.

the parts in the US are really well priced but due to our poor exchange rate and shipping costs its around $400 for all the parts by the time i get them here.

so i really want to be sure I'm going to get some benefits.

otherwise its ....if it aint broke...............
 
When I first got my 97 XJ it didn't sound so great under load. I changed the plugs with copper Champions and then a cap, rotor, and wire set from the dealer. That cured all those problems. The surest way to decide is to pull the front cover and have a look... its time and a Fel Pro gasket kit which costs about $10 here...

A wire set can do funny things. I once had a Subaru that would be noisy less than 1500 RPM. I thought I was lugging it (it was a new to me vehicle) but it was just a bad wire set (even though it was relatively new)... once I changed the wires it was smooth from idle to redline.
 
You can check the timing chain slack by pulling the distributor cap and watching the rotor, then rock the engine back and forth with a breaker bar on the balancer bolt. Make sure you don't loosen the bolt, but if there's slack in the chain, there will be a delay in the distributor rotor changing directions.

Mark
 
Last year my 96 XJ hit the 400,000 mile mark. My friend and mechanic would not help with a motor replacement until it reached that mark.
We did all the normal tests and the engine was ok ,just as you describe yours.
Timing chain stretch was checked electronically by comparing crank and cam phase degrees,which were in sync.We did not open the motor to look at the condition of the chain.
In my case time being the factor- I went with a re-man motor.
Otherwise I would have done a chain,valve job,checked bearings,replaced seals and run it for another couple 100,000.
 
That's 400k kilometres hum that's only 248k miles, when I did our 92 at 200k the chain had no noticeable slack. I've not met too many with timing chain problems 91 up 4.0.

Is the only problem lacking punch up hill. If it's auto trans I had to adjust our downshift kick down cable , all kinds of Wright ups on it. It's near the throttle cables on the top of the motor. It needs to be readjusted every so often. I only adjusted ours a few years ago after a decade of ownership

My first guesses would not be timing chain, I'd look at tune up stuff, sensors or kick down adjustment
 
For what its worth, I pulled the timing cover on my 2001 XJ tonight. It has 337,000 miles and I'm measuring 1/8" deflection in the chain. I believe the service limit is around 3/8"? Can anyone confirm.
 
Looking at my 96 FSM...12.7mm(1/2") or more calls for replacement.
 
For what its worth, I pulled the timing cover on my 2001 XJ tonight. It has 337,000 miles and I'm measuring 1/8" deflection in the chain. I believe the service limit is around 3/8"? Can anyone confirm.

Just wanted to circle back around and correct this.. my 01 XJ had 3/8" slack so I replaced it. It does seem like a big coincidence that both the 97 XJ I bought in 2014 not knowing the previous maintenance history and the 01 XJ that I bought in 2004 and put 300,000 miles on both had the same slack. I know these chains stretch some after they're first installed. Anybody know how much?
 
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